We are investigating both the reactions of hemin with the serum protein hemopexin and the transfer of hemin from serum albumin to hemopexin. Because of the highly aggregated state of hemin in aqueous solution it proves convenient to study the interaction with hemopexin in 40% DMSO/water. These experiments are now nearing completion and we intend extending these studies to aqueous solution by using caffeine to keep the hemin monomeric. The transfer kinetics (hemin from albumin to hemopexin) are much slower in vitro than in vivo, suggesting the presence of catalytic pathways in vivo. We are considering two strategies for this catalysis ligand-mediated pathway and a redox-mediated pathway. Preliminary results suggest that nitrogenous bases (imidazole, histidine, etc.) can compete effectively with serum albumin (but not hemopexin) for hemin and can therefore accelerate the transfer step. Furthermore, we have shown that the reduction of the iron from the plus 3 to the plus 2 oxidation state leads to at least a 10 to the 3rd power enhancement of rate of transfer.